DESCRIPTION: Benzene is an established human carcinogen, however, the mechanisms by which the various benzene metabolites induce mutations are as yet unknown. Exposure to benzene occurs in the environment from auto exhaust, cigarette smoke and chemical manufacturing. The hypothesis advanced by Dr. Singer is that benzene, like other carcinogenic chemicals, yields metabolites which bind to DNA. These adducts can affect base pairing and replication of DNA, leading to mutation and/or lethality. Such effects can be dissected only by examining each adduct individually. The technique of site-directed mutagenesis, using a sequence from a DNA of interest, can furnish answers to many such questions. Dr. Singer proposes to study this problem by reacting several individual deoxynucleosides under a variety of conditions with several benzene metabolites. The adducts will be purified by chromatographic techniques and structurally characterized by UV and NMR spectroscopy and mass spectrometry. Newly isolated adducts will be incorporated into defined sites of oligonucleotides using solid phase synthetic methods. Oligonucleotides containing single modifications will then be studied for effects upon base pairing and DNA replication. These studies will provide new insights into how benzene exposure can lead to toxicity and cancer.